GLUTATHIONE

From Big Medical Encyclopedia

GLUTATHIONE — the tripeptide taking active part in many oxidation-reduction turning into a human body and animals and providing functioning of a number of SH dependent enzymes, C 10 H 17 O 6 N 3 S:

It is eurysynusic in a plant and animal life. Rather large number it contains in a liver, a brain, kidneys and erythrocytes. For the first time G. was allocated from yeast F. Gopkinsom in 1921, however a final structure of this peptide Harrington and Meade (Page R. Harington, T. N. of Mead) established only in

1935 represents white crystal powder with t ° pl 190 ° (with decomposition); let's dissolve in water, it is not alcohol-soluble also ether. During the heating with water G. breaks up with education pyrrolidone carboxylic to - you and a tsisteinilglitsina. Heating in acid medium leads to G.'s disintegration on the amino acids making it.

Feature of a structure of G. is that the rest glutaminic to - you in its molecule form a peptide bond with cysteine at the expense of gamma, but not an alpha carboxyl group as it is peculiar to proteins. The main functional group of G. is the thiol (sulphhydryl) group (SH group) therefore the reduced designation G. as G-SH(G-SH) is eurysynusic. Such sulphhydryl (got into condition) G. easily is exposed to oxidation in both the enzymatic, and non-enzymatic way (under the influence of soft oxidizers, napr, iodine or ferricyanide) therefore the disulfide (oxidized) Form is formed. (— S — S —). This process is reversible:

G.'s biosynthesis happens in various fabrics to high speed. It proceeds in two stages:

It was established that both reactions demand presence of ions of Mg2 + and in certain cases their speed increases in the presence of ions of K+.

Oxidation reaction of the recovered G. is catalyzed by various enzymes differing from each other in specificity in relation to hydrogen acceptors. It is most studied a glutationdegidrogenaz (KF 1.8.5.1), catalyzing hydrogen transfer with G-SH on dehydroascorbic to - that. This enzyme contains in the higher plants and yeast. In a liver of animals the enzymes catalyzing hydrogen transfer with G-SH on disulfide connections are found: on homocystine (glutathione-homocystine — a transhydrogenase; KF 1.8.4.1) and on disulfide group in proteins (a proteindisulfidreduktaza; KF 1.8.4.2). At last, G.'s oxidation can be catalyzed glutathione: poliolnitrit — oxidoreductase (KF 1,8.6.1).

Reverse — recovery of the oxidized G. catalyzes a glutationreduktaz (KF 1.6.4.2), eurysynusic in animal and vegetable fabrics. This enzyme represents the yellow enzyme catalyzing hydrogen transfer with NADF-N or NAD-N on G-S — S-@.

The functional role of G. is big and various. As the active hydrogen carrier it can take part in many redoxreactions, besides, its value and as donor of SH-group is important. Serves as the active group which is directly reacting with substrate in G.'s glitseraldegidfosfatdegidrogenaza. Direct participation of G. in operation at least two cis-a trance isomerases is shown: maleil-acetoacetates-isomerases and maleil-pyruvates-isomerases. The specific role of G. in activity of these enzymes consists that in got into condition he joins substrate on a double bond that leads to formation of saturated compound and allows to be carried out to free rotation:

Is also a coenzyme (see. Coenzymes ) systems of a glioksilaza and formaldegiddegidrogenaza. According to Rapoport (S. Rapoport), G.'s role in protection of hemoglobin against action of various oxidizers and in maintenance of structural integrity of erythrocytes is big.

The states connected with disturbance of exchange of are known patol. At inborn insufficiency of a glyukozo-6-phosphate-dehydrogenase the maintenance of G-SH since the specified enzyme constantly forms NADF-N promoting G.'s preservation in the recovered state decreases. There are forms of a hemolitic disease of newborns, one of the reasons of which is inborn insufficiency in erythrocytes glutathione peroxidases (KF 1.11.1.9), the hydrogen peroxide catalyzing oxidation of the recovered G. On the third month of life a wedge, displays of a disease spontaneously disappear, and insufficiency of enzyme remains.

The form of hemolitic anemia connected with insufficiency of a glutationreduktaza (KF 1.6.4.2), a consequence a cut is described reduction of maintenance of G-SH in erythrocytes is. Also rare hereditary disease — insufficiency of a glutationsintetaza (KF 6.3,2.3) is known. At the same time contents of the general, in blood sharply decreases.

G.'s concentration in blood decreases at some damages of a liver, G.'s Maintenance in blood referred to number of erythrocytes («G.'s indicator») decreases at hyperchromic anemias.

Quantitative definition of G. in biol, material is based on sedimentation of G-SH by salts of cadmium from protein-free extract of fabric. The deposit is dissolved in phosphoric to - those and G.'s number define yodometrichesk. For the general G.'s definition G-S — S-g which is available in test is recovered processing by potassium cyanide or zinc dust.

As medicine G. is not applied.


Bibliography Dzhordzhesku P. and Peunesku E. Biochemical methods of the diagnosis and a research, the lane from Romanians., page 159, Bucharest, 1963; Maister. Biochemistry of amino acids, the lane with English, page 268, 315, M., 1961; Rapoport S. M. Medical biochemistry, the lane with it is mute., page 114, etc., M., 1966; Torchinsky Yu. M. Sulphhydryl and disulfide groups of proteins, page 149, M., 1971; Schröder E. and the Rain orchid To. Peptides, the lane with English, t. 2, page 336, M., 1969; Glutathione, ed. by L. Flohe a. o., Stuttgart, 1974, bibliogr.

B. I. Rozengart.

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